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Updated: May 21, 2026

Bacterial Artificial Chromosomes: A Functional Genomics Tool for the Study of Positive-strand RNA Viruses
Published on: December 29, 2015
Role of JC virus agnoprotein in virion formation
Tadaki Suzuki1, Shingo Semba, Yuji Sunden
1Division of Molecular Pathobiology, Hokkaido University, Research Center for Zoonosis Control, N20, W10, Kita-ku, Sapporo, 001-0020, Japan.
Abstract:
JC virus (JCV) belongs to the polyomavirus family of double-stranded DNA viruses and causes progressive multifocal leukoencephalopathy in humans. JCV encodes early proteins (large T antigen, small T antigen, and T' antigen) and four late proteins (agnoprotein, and three viral capsid proteins, VP1, VP2, and VP3). In the current study, a novel function for JCV agnoprotein in the morphogenesis of JC virion particles was identified. It was found that mature virions of agnoprotein-negative JCV are irregularly shaped. Sucrose gradient sedimentation and cesium chloride gradient ultracentrifugation analyses revealed that the particles of virus lacking agnoprotein assemble into irregularly sized virions, and that agnoprotein alters the efficiency of formation of VP1 virus-like particles. An in vitro binding assay and immunocytochemistry revealed that agnoprotein binds to glutathione S-transferase fusion proteins of VP1 and that some fractions of agnoprotein colocalize with VP1 in the nucleus. In addition, gel filtration analysis of formation of VP1-pentamers revealed that agnoprotein enhances formation of these pentamers by interacting with VP1. The present findings suggest that JCV agnoprotein plays a role, similar to that of SV40 agnoprotein, in facilitating virion assembly.
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